Interrater Reliability of 99mTc-DMSA Scintigraphy Performed as Planar Scan vs. SPECT/Low Dose CT for Diagnosing Renal Scarring in Children

Abstract

^99mTc-dimercaptosuccinic acid (DMSA) scintigraphy is currently the method of choice for assessing renal scarring in children, but it is not established whether conducting the scan as a single photon emission tomography combined with low-dose CT (SPECT/ldCT) scan provides additional diagnostic benefits when compared to conventional planar scintigraphy. In the present study, we evaluated the interrater reliability of DMSA SPECT/ldCT vs. planar DMSA scintigraphy for diagnosing renal scarring.

Methods: Two nuclear medicine physicians blinded to patient data retrospectively analysed all paediatric ^99mTc-DMSA scintigraphes that were conducted in our department for the assessment of post pyelonephritis renal scarring between 2011 and 2016. All scintigraphies included both a planar scan and SPECT/ldCT, and were performed on either a Phillips Precedence 16 slice CT or a Siemens Symbia 16 slice CT. The readers were blinded to each other's readings and to patient data, and assessed all scans dichotomously for evidence of renal scarring. For each scan, the readers further noted if they were confident in their interpretation.

Results: A total of 46 pairs of planar SPECT/ldCT DMSA scans were included. The readers were unconfident about their interpretation of 40% of the planar scans and 5% of the SPECT/ldCT scans. The interrater agreement rate was 72% for planar scans and 91% for SPECT/ldCT, and the corresponding Cohen's kappa values were 0.38 and 0.79.

Conclusion: DMSA SPECT/ldCT is associated with higher reader confidence and interrater reliability than conventional planar DMSA scintigraphy for the assessment of post pyelonephritis renal scarring in children.

Keywords: kidney disease; kidney function; paediatric; pyelonephritis; renal scarring.

Figure 1

^99mTc-dimercaptosuccinic acid ^99mTc-DMSA scintigraphy as planar scan and SPECT/low-dose CT (SPECT/ldCT) in a 13-year-old boy. Evaluation scan conducted 3 months after pyelonephritis. On the planar scintigraphy, two defects that are suspicious of infarction are evident on the lateral and upper pole of the right kidney. However, when supplementing with SPECT/low-dose CT, additional infarction is unveiled in the left kidney not seen on planar scintigraphy. Upper panel: SPECT (left), SPECT/ldCT (right). Lower panel: planar scan, posterior view (left), anterior view (middle), geometric view (right).

Figure 2

^99mTc-DMSA scintigraphy as planar scan and SPECT/low-dose CT (SPECT/ldCT) in a 10-year-old girl. Evaluation scan conducted 3 months after pyelonephritis. Planar scintigraphy shows an atrophic left kidney and a normal right kidney with a small defect that was interpreted as persistent foetal lobulation due to incomplete fusion of the developing renal lobules. However, SPECT/low-dose CT shows that the defect is due to scarring, since cortical atrophy and irregular scarring are seen on CT. Upper panel: SPECT (left), SPECT/ldCT (right). Lower panel: planar scan, posterior view (left), anterior view (middle), geometric view (right).